package demo;

public class MySingleList implements List{
    public class ListNode{
        public int val;
        public ListNode next;
        public ListNode(){

        }
        public ListNode(int val){
            this.val = val;
        }
    }
    public ListNode head;
    @Override
    public void addFirst(int data) {
    ListNode node = new ListNode(data);
    if(head == null){
        head = node;
        return;
    }
    if(head != null){
        node.next = head;
        head = node;
    }
    }

    @Override
    public void addLast(int data) {
    ListNode node = new ListNode(data);
    ListNode cur = head;
    if(head == null){
        head = node;
        return;
    }
        while(cur.next != null){
            cur = cur.next;
        }
        cur.next = node;
    }


    @Override
    public void addIndex(int index, int data) {
    ListNode node = new ListNode(data);
    checkPos(index);
    if(index == 0){
        addFirst(data);
        return;
    }
    if(index==size()){
        addLast(data);
        return;
    }
    ListNode cur = findIndex(index);
    node.next = cur.next;
    cur.next = node;

    }
    private ListNode findIndex(int index){
        ListNode cur = head;
        int count = 0;
        while(count != index -1){
            cur = cur.next;
            count++;
        }
        return cur;
    }
    private void checkPos(int index){
        if(index < 0 || index > size()){
            throw new checkPosException("下标不合法");
        }
    }
    @Override
    public void remove(int key) {
    if(head == null){
        System.out.println("链表为空，无法清除");
    }
    if(head.val == key){
        head = head.next;
    }
    ListNode cur = search(key);
    if(cur == null){
        System.out.println("没有你要删除的数字");
    }else{
        ListNode del = cur.next;
        cur.next = del.next;
    }
    }

    private ListNode search(int key){
        ListNode cur = head;
        while(cur.next != null){
            if(cur.next.val == key){
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }
    @Override
    public void removeAll(int key) {
        if (head == null) {
            return;
        }
        ListNode prev = head;
        ListNode cur = head.next;
        while (cur != null) {
            if (cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            } else {
                prev = cur;
                cur = cur.next;
            }
            if (head.val == key) {
                head = head.next;
            }
        }
    }

    @Override
    public void clear() {
        head = null;
    }

    @Override
    public int  size() {
        ListNode cur = head;
        int count = 0;
        while(cur != null){
            count++;
            cur = cur.next;
        }
        return count ;
    }

    @Override
    public void display() {
    ListNode cur = head;
    while(cur != null){
        System.out.print(cur.val +" ");
        cur = cur.next;
    }
        System.out.println();
    }
}
